This invention relates to latch release mechanisms for use with vacuum interrupters within transformer tap changer assemblies. The tap changer assembly consists of a tap selector and contactor, with the vacuum interrupter mounted on an insulating panel and connected with a motor drive mechanism. The mechanism is operated through a plurality of gears and cams coupled with the tap-selector assembly. When changing from one tap position to the next the mechanical arrangement of parts coupled to a motor drive temporarily provides interruption of the current in one of two paths by opening the vacuum interrupter contacts.
Atmospheric pressure plus the static insulating oil head pressure keep the vacuum interrupter in its normally closed position. One currently employed interrupter latch mechanism consists of a slideably connected latch and catch arrangement wherein a rectilinear step on the latch assembly retains the catch against the force of the trigger spring. In operation of the latch release cycle, the latch is slideably removed from under the catch so that the trigger spring moves the catch lever as soon as the rectilinear step is clear of the catch. Since the latch assembly moves in a horizontal plane a decreasingly smaller portion of the step must support the entire force of the trigger spring. If trigger spring forces are increased the step assembly could become worn, after long periods of continued use, by the mechanical pressure exerted upon the step during the last few fractions of an inch of motion of the latch release cycle. A catastrophic result could occur when the step portion becomes worn to such and extent as to be incapable of retaining the catch and so causing the vacuum interrupter to become interrupted prematurely.
The purpose of this invention is to provide a vacuum interrupter latch release mechanism wherein the latch assembly remains virtually unworn over an indefinite period of operating time.